The present invention relates to an arrangement for the preparation of the fuel-air mixture for an internal combustion engine operating under variable conditions and more specifically to an arrangement having a controlling jet for the fuel in the induction manifold.
In the preparation of the fuel-air mixture it is important that the fuel entering the induction manifold be so finely divided that, for example, only particles of a size under 10 microns be present.
To this end, there are known devices containing means for effecting good atomization of the fuel. However, the disadvantage of these devices was that while single small particles under 10 microns in size were attained, over all an insufficiently fine mist was created to provide complete combustion. Complete combustion must be attained if condensate formation in the induction manifold is to be avoided and proper filling of the cylinders is to be provided. Further, heretofore known devices were constructed such that only during one portion of the operating range, for example, idling conditions, or part load conditions, or full load conditions, was a good treatment of the fuel-air mixture achieved.
It is, therefore, the object of the present invention to provide an arrangement for preparing the fuel-air mixture so as to attain extremely small particle size of the fuel over the entire operating range of the engine, resulting in complete or nearly complete combustion.
To this end, the fuel openings of a known device, for example, a venturi-pipe, Laval-nozzle, and the like, are arranged so that the fuel-air mixture being drawn in, usually by manifold vacuum, approaches sonic velocity in the region of the arrangement of the present invention. While it has heretofore been attempted to attain better preparation of the fuel-air mixture through raising its speed, the use of extremely high speeds, approaching sonic velocity, has not been attempted. Through such extremely high speeds, a tearing of the fuel particles into extremely fine particles, that is, under 10 microns in size, and an intimate mixing with the intake air will be attained. As a result, a heretofore unknown thorough and almost residue free burning of the induction fuel-air mixture and proportionate filling of the cylinders is possible.
A further feature of the present invention consists in the provision of a device for the production of sonic velocities for the mixture under idling and partly loaded conditions.
In accordance with the present invention, the operating range of the internal combustion engine is broken down into various operating regions. Conditions established in the idling condition range are utilized to overcome other conditions in the part load and full load range, that is, the device produces small quantities of intake air at sonic velocity which are utilized to achieve improved operation in the part load and full load ranges.
Accordingly, a further feature of the invention is the provision of a device for the preparation of the idle mixture directly in the induction manifold and having means for part load operation above or upstream of the idle mixture device in the flow direction of the intake air.
The opening for the preparation of the idle mixture lies in the induction manifold but minimal control of this mixture in the cylinder is sufficient to prevent the deposit of condensate particles because of the small requirements of fuel and air from the device containing the opening.
In order to reduce cost and space requirements it is desirable that the sonic velocity in the device be produced through the induction vacuum of the motor. This vacuum depends on operating condition changes so that the production of the sonic velocity in the device of the present invention is responsive thereto. It is also possible to utilize superchargers, or similar means, to produce the sonic velocity, by means of which the additionally flowing air assists in the production of the sonic velocity while if the design so permits, the pressure atomizes the fuel.
A preferred embodiment of the invention is a vacuum operated device in which the passages, channels, or other structures for the mixture formation by injection at different areas are formed so that in the flow direction, first a converging, then a parallel, and finally a diverging passages or spaces are presented. By this configuration high flow velocities and mixing is obtained and achievement of the purposes of the invention is assured.
It has been found that the use of the parallel passage portions referred to above, while desirable, are not essential and the passages, channels, or other structures may be formed so as to present, in the flow direction, first a converging and then a diverging passages or spaces. The parallel space may be dispensed with when, for example, small fuel particle size is not absolutely necessary.
In another aspect of the invention, a ring like passage is formed about a fuel nozzle for opening in the device. Through this passage, all or almost all of the air necessary for idling operating is provided. In the narrow portion of the passage the nozzle is positioned.
In yet another aspect of the present invention a flat plate is positioned opposite a fuel nozzle or opening to provide still more intimately mixing of the already small fuel particles with the intake air.
The nozzle opening may be provided with a needle valve regulating apparatus or the like. It will be appreciated that one or more nozzle bodies may be employed having one or more nozzle openings with the associated sonic velocity producing structure.
A still further aspect of the present invention contemplates the provision of a fuel injection nozzle body in an air entrance passage having a throttle valve. The throttle valve may be regulated so that sufficient intake air is provided to attain sonic velocity in the air passage. In the alternative, a carburetor may be employed in lieu of the injection nozzle body. Additionally, air entrance passages having one or more openings to the atmosphere and appropriate regulating throttle valves may be employed to provide additional intake air to the above described apparatus necessary to meet operating requirements in the above part load to the full load ranges. The control of the air passages may be coordinated by a mechanism which first operates the throttle valve associated with the device for producing sonic velocity and thereafter operates the throttle valve for the aforesaid additional air passages.
With the present invention exhaust gas in amounts of from 10% to 20% of the intake air may be supplied in the latter, thereby reducing the nitric oxide content of the engine emissions.